1. Technical Field
The present invention relates to a technology for verifying validity of contents, especially to a technology for reducing processing load involved in such a verification.
2. Background Art
Means to prevent fraudulent acts involving illegal copying, falsification, and replacement of contents include applying signature information indicating that the contents have been issued by a legitimate right holder as well as distributing, together with the contents, verification information for verifying whether the contents include unauthorized contents in which falsification and the like have been made.
Patent Reference 1, being one example of such means, discloses a technology for verifying validity of contents by distributing signature information, verification information, and contents via network. According to the technology, authentication information including signature information of a transmission source and verification information for checking consistency of individual partial contents constituting the contents is transmitted to an executing device in advance of transmission of the contents. When receiving the authentication information, the executing device verifies the signature information included therein. If the verification of the signature information is successful, the executing device receives and plays the contents. In parallel with the playback, the executing device repeats the verification of consistency of the individual partial contents by using the verification information, and stops the playback when the verification fails.
Even if the executing device has received contents including unauthorized contents, the technology enables the executing device not to start playback of the contents or to stop the playback in the middle.    [Patent Reference 1] U.S. Pat. No. 6,480,961;    [Patent Reference 2] Japanese Laid-Open Patent Application Publication No. 2002-281013;    [Nonpatent Reference 1] http://positron.jfet.org/dvdvideo.html (Accessed 17 May 2004);    [Nonpatent Reference 2] http://www.pioneer.co.jp/crdl/tech/mpeg/1.html (Accessed 17 May 2004);    [Nonpatent Reference 3] “The Art of Computer Programming Vol. 2 Seminumerical Algorithms” written by Donald E. Knuth, ISBN: 0-201-03822-6; and    [Nonpatent Reference 4] “Joho Security (Information Security)” written and edited by Atsuko Miyaji and Hiroaki Kikuchi, and compiled by Information Processing Society of Japan.
According to the conventional technology described above, however, the executing device has to continue verifying the verification information in parallel with the playback, and therefore there is, a problem that processing load of the executing device becomes high during the contents playback.
Furthermore, from a safety standpoint, it is also often the case that encoded contents are distributed, instead of contents. In such a case, the executing device has to also conduct decryption processing in parallel, and thus the processing load increases even more.
Accordingly, the executing device has to be equipped with a highly efficient processor operable to conduct these processes in parallel.
The present invention solves these problems, and aims at offering a data processing device, a data processing method, a data processing program, and a recording medium that achieve hindrance-free contents playback, even if the equipped processor is poorly efficient, by reducing processing load of the executing device during the contents playback.